The invention relates to an adjusting device for adjusting the resultant static moment of unbalanced-mass vibrators for the generation of directed oscillations, said static moment being generated by at least two pairs of unbalanced-mass part-bodies adjustable relative to one another over a relative adjustment angle xcex2. A particular generic type of adjusting devices for unbalanced-mass vibrators for the generation of directed oscillations is described in the document EP 0 506 722 B1 to be included in the general prior art. For the sake of simplification, the terms used in said publication, namely the unbalanced-mass part-bodies and the centrifugal part-forces (or centrifugal part-force vectors), assigned to them, the unbalanced-mass part-bodies of one type and the other and the xe2x80x9cpairxe2x80x9d of unbalanced-mass part-bodies, have been adopted in the subsequent description of the present invention. In accordance with the publication mentioned, the relative adjustment angle xcex2 (subsequently called phase angle xcex2) is also defined below in such a way that the value xcex2=180xc2x0 corresponds to a zero amplitude of oscillation and the value xcex2=0xc2x0 corresponds to a maximum amplitude of oscillation.
The phase angle xcex2 is theoretically defined between the centrifugal part-force vectors of the individual unbalanced-mass part-bodies of one type and the other of a xe2x80x9cpairxe2x80x9d of unbalanced-mass part-bodies. In practice, the phase angle xcex2 may also be defined between features (for example, geometric features) of the unbalanced-mass part-bodies of a pair, insofar as the position of the mass center of gravity of the eccentric mass is known. The identification xe2x80x9cMRxe2x80x9d is used for the reaction torques xe2x80x9cMRxe2x80x9d which, in the case of a phase angle xcex2xe2x89xa0180xc2x0, occur twice as alternating moments during each unbalanced-mass revolution through the angle of rotation xcexc=2xcfx80 on the shafts of the unbalanced-mass part-bodies [these alternating moments have a sinusoidal profile with two minimum and two maximum values per revolution of the unbalanced-mass part-body].
The average reaction torques which act in only one direction and which can be calculated by integrating MR(xcexc) against the angle of rotation xcexc=2xcfx80 and by subsequently dividing the integration value by 2xcfx80 are designated here by xe2x80x9cMRQxe2x80x9d. As a person skilled in the art may gather, for example, from the document EP 0 506 722 B1, in the case of a set phase angle 0xc2x0 less than xcex2 less than 180xc2x0, these average reaction torques MRQ [which themselves then represent a function of the phase angle xcex2, hence: MRQ(xcex2)] act on the unbalanced-mass part-bodies of a pair in such a way that the reaction torques MRQ of one type seek to accelerate the rotation of the unbalanced-mass part-bodies of one type and that the reaction torques MRQ of the other type seek to decelerate the rotation of the unbalanced-mass part-bodies of the other type. In an unbalanced-mass vibrator according to FIG. 1 of the description of the invention, the result of this mode of operation, insofar as said vibrator were to operate in idling mode with a phase angle of, for example, xcex2=90xc2x0, would be that the motor M2 would have to operate in a motive way and the motor M1 in a generative way, both motors (taking into account the output due to bearing friction) converting part of their power as apparent power. The operation of vibrator motors working with apparent powers is also clearly illustrated in FIG. 2 of the document WO 97/19765 likewise included in the general prior art (it should be noted that this has a different definition of the phase angle xcex2 such that, here, xcex2=0xc2x0 is equated to an amplitude of oscillation=zero). It is pointed out at this juncture that a person skilled in the art is also aware of other designations, such as, for example, xe2x80x9ccentrifugal momentxe2x80x9d or xe2x80x9cunbalance momentxe2x80x9d, for the designation xe2x80x9cstatic momentxe2x80x9d.
Furthermore, the present invention relates, in particular, to that generic type of piledriving vibrators which are adjustable in terms of their static moment and operate at high working rotary frequencies and which are designed for a particular operating mode such that, when they are used for work, the excitation of resonant frequencies fR lying below the working rotary frequency fo of the vibrator is to be avoided. In the directional vibrators which come under consideration for this operating mode, it is possible, by means of their control devices, during the rotation of the vibrator (in addition to the setting of any desired resultant static moments) to set selectively two particular resultant static moments: the setting of a xe2x80x9cminimum positionxe2x80x9d with a minimum resultant static moment for the generation of an amplitude of oscillation equal to zero and the setting of a xe2x80x9cmaximum positionxe2x80x9d with a maximum resultant static moment for the generation of a maximum amplitude of oscillation. The particular operating mode works as follows: adjustment of the phase angle to the minimum position when the vibrator is at a standstill. Running up of the vibrator in the set minimum position to the working rotary frequency fo. Adjustment of the phase angle to the maximum position and execution of the vibration work. Adjustment of the phase angle to the minimum position. Reduction of the rotary frequency of the vibrator from the working rotary frequency to zero, with the minimum position being maintained. The particular operating mode last described is also to be referred to below by the designation xe2x80x9cresonance avoidance operating modexe2x80x9d.
Two generic types of adjustable vibrators are known for executing an operating mode such as that described above. One generic type, which is described, for example, in EP 0 473 449 B1 or in EP 524 056 B1, works, for the purpose of adjusting the phase angle, with a mechanical variable-ratio gear unit, by means of which there is always a torque-transmitting connection of the unbalanced-mass part-bodies of one type to the unbalanced-mass part-bodies of the other type via the variable-ratio gear unit. In the other generic type of xe2x80x9cmotively adjustable vibratorsxe2x80x9d, the adjustment of the phase angle is brought about without a variable-ratio gear unit, specifically using adjusting motors which may at the same time also be working motors. The present invention is to be attributed to the last-mentioned generic type, since, in it, the adjustment of the phase angle is carried out, with drive motors also being included.
Insofar as the motively adjustable vibrators are intended, with the aid of a closed control loop and an angle measuring device, to make it possible to set and hold the phase angle continuously at any predeterminable value between xcex2=180xc2x0 and xcex2=0xc2x0 (as is provided, for example, in the case of EP 515 305 B1, EP 0 506 722 B1 and WO 97/19765), they are indeed suitable for executing the xe2x80x9cresonance avoidance operating modexe2x80x9d, but they have the disadvantage that they are highly cost-intensive and that, in practice, it is not yet possible in a satisfactory way to regulate the phase angle in the range of about xe2x88x9290xc2x0 less than xcex2 less than +90xc2x0. This is connected with the profile of the function of the reaction torque MRQ(xcex2) or of the dependent necessary motor torque MD(xcex2) in dependence bn the phase angle xcex2 (with a positive curve gradient in an angular range of about 0xc2x0 less than xcex2 less than 90xc2x0 and with a negative curve gradient in the angular range of about 90xc2x0 less than xcex2 less than 180xc2x0), as may be gathered, for example, from FIG. 2 of WO 97/19765. Another disadvantage is that, when the continuous regulation of the phase angle xcex2 is used even when the intention is to work only in the maximum position (point E or Exe2x80x2 in FIG. 2 of WO 97/19765), during the run through the entire range of adjustment of the phase angle xcex2 the motors have to be loaded with far higher torques than is necessary for the maximum position.
If two further solutions are considered, which are disclosed by DE 44 39 170 A1 and WO 94/01225 and in which the adjustment of the phase angle xcex2 is likewise to be possible, with drive motors being included, and in which it is to be possible to set a phase angle without a complicated measuring and regulating device, it can be established, in general terms, that the adjusting devices for adjusting the phase angle xcex2, which are provided there and operate without a closed control loop, are, of course, all the more unsuitable for setting a phase angle xcex2 in the range of about xe2x88x9290xc2x0 less than xcex2 less than +90xc2x0. Moreover, these solutions lack the capacity for executing a xe2x80x9cresonance avoidance operating modexe2x80x9d. A closer look also makes it possible to establish the following:
The vibrator presented in DE 44 39 170 A1 relates to a quite specific type of generation of a directed resultant centrifugal force, specifically using at least 3 pairs of unbalanced-mass part-bodies with at least 6 individual unbalanced-mass part-bodies. This configuration results in a series of still unknown physical effects in the case of a vibrator of adjustable phase angle (as shown in DE 44 39 170 A1) For example, the behavior of this vibrator, xe2x80x9cas regards the question of whether and, if so, with what effects reaction torques occurxe2x80x9d (column 4, lines 36-38). How a regulation of the phase angle by means of such effects, particularly also in the range xe2x88x9290xc2x0 less than xcex2 less than +90xc2x0, could be completed is left open in the description. The statements on the object of the invention (column 4, lines 46+) say, in general terms, that the use of hydraulic motors as drive motors and servomotors is to take place only in conjunction with controllers, so that any predetermined values for the relative adjustment angle can be set (this, however, presupposes the existence of a measuring system). In the event that the vibrator were to be operated only by regulation, using a closed control loop, a vibrator according to DE 44 39 170 A1 would have to be included in the last-described generic type of vibrators which is also capable of executing the xe2x80x9cresonance avoidance operating modexe2x80x9d.
However, as expressed in the statements in column 8, lines 49 to 56, a control of the phase angle (open control circuit) is also to be possible. In that case this control, to which the control line 80 issuing between the series-connected motors 40 and 42 also refers, would have to function in the particular way described in the publication DE 43 01 368 (corresponding to WO 94/01225) mentioned there. This particular way also includes, inter alia, the fact that an adjustment of the phase angle xcex2 is only possible in the range 90xc2x0 less than xcex2 less than 180xc2x0 (according to the angle definition of the present invention).
A stop for limiting the phase angle xcex2 for the purpose of setting a minimum amplitude not to be undershot is provided, so that, if the motor regulation fails, a further variation in the phase angle can be prevented by means of constraints. This is carried out because, in the event of a set genuine zero amplitude, the rolling bearings of all the unbalanced-mass shafts would be damaged. However, this stop does not serve for maintaining the phase angle xcex2 as a minimum position along the lines of the xe2x80x9cresonance avoidance operating modexe2x80x9d when the vibrator is run up from a standstill to the working rotary frequency. A stop is likewise provided for setting the maximum amplitude, but only in an emergency when the normal regulating device for the phase angle xcex2 fails. It should also be noted that this document has a different definition of the phase angle xcex2 such that xcex2=0xc2x0 would have to be equated to an amplitude of oscillation=zero.
The publication WO 94/01225 may be considered as the nearest prior art: it should be noted that, in this document, contrary to the definition of the present invention, the phase angle xcex2 is fixed such that xcex2=0xc2x0 corresponds to a zero amplitude. As may be gathered, for example, from FIG. 1, in the vibrator described there each unbalanced-mass part-body is to be driven by its own motor, in each case two hydraulic motors which belong to different unbalanced-mass part-bodies being connected in series. A very special activation of the motors (with an open control circuit), which is suitable only for a series connection, comes under consideration for the purpose of varying the phase angle. In this case, however, simply for safety""s sake, the gearwheels connected to the unbalanced-mass part-bodies 101 and 102 and meshing with one another are to come into operation in the event that the synchronization to be carried out in principle by the motors is disrupted by other disruptive forces. A stop 228/213 shown in FIGS. 2 and 3 is to serve, in particular, for ensuring that a phase angle of xcex2=90xc2x0 is not exceeded. This limitation of the phase angle is necessary, here, as a safety measure, because regulation with a closed control loop is not provided for this vibrator, and because the range of a phase angle xcex20xc2x0 less than xcex2 less than 90xc2x0 (according to the angle definition of the present invention) is, here, a range which cannot be controlled and is therefore ruled out [page 7, lines 1 to 21; page 11, lines 9 to 21].
For this reason, this design must also take into account the disadvantage that, even in the case of a phase angle of xcex2=90xc2x0, the desired maximum resultant static moment must be achieved, thus presupposing the use of greater unbalanced masses and leading to unnecessarily high bearing forces. Another disadvantage of the vibrator shown here is the extremely asymmetric load on the motors. In the case of a stop phase angle of xcex2=90xc2x0, taking into account the xe2x80x9csum pressurexe2x80x9d, the first motors are subjected to more than two and a half times the load of the second motors. In this case, the xe2x80x9csum pressurexe2x80x9d is the sum of the input pressure and output pressure of the motor, this sum being critical for the service life of the motors.
A further disadvantage is the fact that an unequivocal relationship between the adjusting torques of the servomotors and the relative adjustment angles xcex2 set as a result is afforded only when the vibrator oscillates at a uniform rotary frequency, with a constant useful power being transmitted at the same time. Insofar as the amount of one of the last-mentioned variables changes in an unpredetermined way, as may occur when piledriving vibrators are used, the use of regulation is necessary for setting or maintaining a predetermined relative adjustment angle xcex2. That is to say, in this case, a feedback of the actual position of the rotary angles of the unbalanced-mass part-bodies is still necessary in order to set and hold the relative adjustment angle xcex2 at a predetermined value (as a result of which, this vibrator would again have to be included in the last-described generic type in which any predeterminable phase angle xcex2 can be set by means of a closed control loop.). As regards the vibrator according to the present invention, however, it is demanded that the intended mode of operation be capable of being carried out, even in the case of changed values for the rotary frequency and for the useful work converted.
The object of the present invention is to improve the abovementioned state of the art of vibrators with motive angle adjustment, so that, in the case of vibrators of different design, an adjustment of the static moment between a minimum position and a maximum position can be implemented more simply and more cost-effectively, while it is also to be possible to execute the xe2x80x9cresonance avoidance operating modexe2x80x9d.
The solution for achieving the object is defined by the independent patent claims 1 and 7, patent claim 7 being concerned with that special design variant of the invention in which two hydraulic motors hydraulically connected in series are involved in the adjustment of the phase angle, the phase angle being capable of being set only in the range +90xc2x0 less than xcex2 less than +180xc2x0. These two claims are based on the common principle that the adjustment of the phase angle xcex2 from a minimum position to a maximum position is brought about by the action of cutting in an adjusting braking torque and/or adjusting acceleration torque which acts on the unbalanced-mass part-bodies and as a result of the effect of which the unbalanced-mass part-bodies of different type are rotated relative to one another in an uninterrupted adjustment movement, until the adjustment movement is necessarily terminated as a result of the contacting of two stop faces of a stop and the maximum position is consequently set. Further advantageous developments of the invention are described in the subclaims.
Particular advantages in the use of the invention are also exhibited with regard to the following features: the outlay is reduced, in particular, because a closed control loop is dispensed with. A reduction in the maximum motor load is achieved, with the result that motors having smaller dimensions can be employed. The problem of the regulatability of the phase angle in the range xe2x88x9290xc2x0 less than xcex2 less than +90xc2x0 is avoided. An automatic operating mode of the vibrator, irrespective of the set working rotary frequency and of the useful power transmitted, can be ensured, specifically without the use of a closed control loop for the phase angle xcex2. The adjustment from a minimum position to a maximum position (and vice versa) can be carried out extremely quickly. Where hydraulically operated motors are concerned, open and closed circulation may be employed. If hydraulic motors not connected in series are used, the provision of a special energy source for carrying out the angle adjustment may be dispensed with.
The invention is explained in more detail, using FIGS. 1 to 4, by means of four examples of vibrators according to the invention with hydraulically operated motors, FIGS. 1 to 3 each containing two part-drawings for illustrating the different switching states of the hydraulic circuit prior to the adjustment and after the adjustment of the resultant static moment from a minimum position to a maximum position. Of these figures: